[2] He took part in the several cruises with the escadre d'évolution, and was promoted to Lieutenant March 1779.
[3] In 1779, Mortemart was given command of the 26-gun frigate Aigrette, part of the squadron under Orvilliers.
[2] On 11 September 1781, along with Aigrette, under Traversay, he took part in the capture of HMS Iris and Richmond,[2] which the French Navy took in service as Richemond.
[7] Mortemart was given command of Richemond, which he captained at the Battle of the Saintes in 12 April 1782, where she attempted to tow Glorieux to safety before being ordered to retreat.
He was then promoted to Captain, aged just 25, and given command of the 40-gun frigate Nymphe, to cruise off Martinique with the 32-gun Amphitrite.